Halogen lamp with internal molybdenum parts

ABSTRACT

A regenerative cycle incandescent lamp containing bromine or iodine as a halogen has a mount structure all of which is made of a highly ductile molybdenum. The particular molybdenum has a percentage of elongation which is greater than 20%.

United States Patent 1 Danko HALOGEN LAMP WITH INTERNAL MOLYBDENUM PARTS[75] Inventor: George K. Danko, Bedford Heights,

Ohio

[73] Assignee: General Electric Company,

Schenectady, NY.

[22] Filed: June 21, 1974 21 Appl. No.: 481,662

[52] US. Cl. 313/222; 313/271; 313/318 [51] Int. CL ..H01K 1/20; HOlK1/50 [58] Field of Search 313/222, 178, 271, 318,

[56] References Cited UNITED STATES PATENTS TJampens et al 313/222 XOct. 14, 1975 3,538,373 11/1970 van der Linden et a1. 313/222 X3,681,640 8/1972 Martin 313/222 3,798,491 3/1974 Malm 313/222 X3,829,729 8/1974 Westlund, Jr. et a1 313/222 X Primary ExaminerPalmer C.Demeo Attorney, Agent, or Firm-Ernest W. Legree; Lawrence R. Kempton;Frank L. Neuhauser 57 ABSTRACT A regenerative cycle incandescent lampcontaining bromine or iodine as a halogen has a mount structure all ofwhich is made of a highly ductile molybdenum. The particular molybdenumhas a percentage of elongation which is greater than 20%.

6 Claims, 1 Drawing Figure us. Patent 0ct.14,1975 3,912,960

HALOGEN LAMP WITH INTERNAL MOLYBDENUM PARTS BACKGROUND OF THEINVENTION 1. Field of the Invention The invention relates generally toregenerative cycle incandescent lamps. More particularly, the inventionrelates to the use of highly ductile molybdenum internal lamp partswhich are used in a lamp containing a halogen gas such as iodine orbromine.

2. Description of the Prior Art Incandescent tungsten-halogen lamps werefirst disclosed in Fridrich et al U.S. Pat. No. 2,883,571. These lampsemployed iodine as a regenerative cycle agent to remove evaporatedtungsten from the bulb wall and redeposit it on the tungsten filament.Other internal lamp parts such as filament supports and inner lead-inconductors were also made of tungsten.

Because tungsten is brittle and slightly more expensive than otherrefractory metals, efforts have been made to replace tungsten innerleads and filament supports. One of the replacement metals which hasbeen tried is molybdenum.

The types of molybdenum tried as substitutes are commercially known asType R molybdenum, 99.95% molybdenum, and Type KW molybdenum, 99.90%molybdenum. Although these molybdenum substitutes were less expensivethan tungsten, they were comparatively brittle having a percentageelongation which varied between 6 and 10%. With this degree ofbrittleness, or lack of ductility, it was difficult to manufacture lampsusing this type of molybdenum on high-speed equipment. It was found thata high percentage of the molybdenum parts used on the high-speedequipment would fracture from the cold-working processes associated withautomated manufacturing techniques.

SUMMARY OF THE INVENTION It is therefore an object of the invention tomanufacture a halogen lamp which uses a highly ductile refractory metalfor internal lamp parts. A further object of the invention is to use arefractory metal which costs less than tungsten. Still another object ofthe invention is to use a ductile refractory metal which can becoldworked on high-speed production equipment, thereby decreasing thecost of the lamp. Yet another object of the invention is to make ahalogen lamp without tungsten inner parts and still maintain theenvelope wall free of discoloration.

Briefly stated, the objects of the invention are accomplished by makinginternal lamp parts of a highly ductile molybdenum, with a minimumpercent elongation of approximately for use in a bromine or iodineregenerative cycle lamp. In one embodiment utilizing the particularwire, the level of bromine is controlled within certain limits to make alamp. The observed range of bromine is from 0.025 to 0.075% of theenvelope volume. A lamp having a concentration of bromine above 0.075shows attack of the molybdenum lamp parts which can cause prematurefailure; whereas, the use of less than 0.025% of bromine causes wallblackening after several hours of operation presumably because there isan insufficient amount of halogen present to carry the tungsten from thebulb wall back to the filament.

The molybdenum wire used in the invention is sufficiently ductile andcan be cold-worked without fracturing or embrittlement. This propertymakes it possible to manufacture the lamp mount and the lamp itself onhigh-speed automatic equipment. Previously, tungsten and KW molybdenumand R molybdenum parts required heating before they could be formed toavoid fracture problems. Heating necessarily slowed down themanufacturing process and made lamps of this type less adaptable tohigh-speed equipment.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is aperspective view of the lamp of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, lamp10 therein illustrated is a form of a tungsten-halogen lamp of theinvention. The lamp is comprised of an envelope 1 1 which is made of avitreous material, such as quartz or 96% silica known as Vycor, atungsten filament 12 which is part of mount 13, tipped-off residue 14,and pinch seal 15. Mount 13 is further comprised of filament 12, lead-inconductors l6 and 17, bridge 18, and support 19. Lead-in conductor 16has an outer lead wire 20, thin molybdenum foil portion 21, and longinner lead wire 22. All of the internal metal parts, other than thetungsten filament, are made of highly ductile molybdenum.

Lead-in conductor 17 also has an outer lead wire 23, thin molybdenumportion 24, and a short inner lead 25. Both lead-in conductors are heldin fixed relation to each other by bridge 18 which also holds filamentsupport 19.

A commercial embodiment using the lamp illustrated in the drawing is aPAR 38 reflector lamp which uses the halogen lamp inside a reflector andcover. This lamp operates at 250 watts, volts for approximately 4000hours and has an initial lumens-per-watt rating of 17.0. In themanufacture of the lamp illustrated in the drawing, the mount 13 is heldin fixed relationship to the envelope 11, and fires (not shown) areapplied to the envelope in the area of pinch seal 15. Pinch jaws, alsonot shown, then squeeze the molten glass together to form a hermeticseal with molybdenum foils 21 and 24. After the envelope is pinchsealed, the lamp is flushed and filled with a gas mixture through anexhaust tube, the tipped-off residue of which is shown at 14. The fillgas used to make this particular lamp is one which contains 12%nitrogen, 87.950% argon, and 0.050% Ch Br, at a pressure of 3000 i 300torr.

An automated process for making mount 13 is' more fully described inpatent application Ser. No. 424,875 assigned to the assignee of thepresent invention. Briefly stated, the inner leads 22 and 25 arepreformed by cold-working molybdenum wire to give the desired length andother geometry. These leads are then secured to bridge 18 along withsupport 19. Spiral 30 of support 19 is open at this point in theprocessing. Coil 12 is then clamped to the respective inner leads and istensioned by elongating inner lead 22 which has a bend, not shown, atlocation 31. Following this, the spiral is closed around the filament,and the inner leads are connected to molybdenum foils 21 and 24 andouter leads 20 and 23.

As shown at locations 26 and 27, the molybdenum is bent by cold-workingto make the proper configuration for inner lead 22. Inner lead 22 alsocontains a tensioning bend, not shown, at what is designated as location31. Inner lead 25 also requires several bends as illustrated atlocations 28 and 29. Ordinarily, if tungsten parts were used, such bendswould require heat treatment, or if done in a cold state, the partswould most likely fracture. This is also true of the standard grades ofmolybdenum wire which have a percentage elongation between 6 and 10%.

Using the molybdenum wire of the invention which has a minimum of 20%elongation, it becomes relatively easy to make the bends and do variousflattening and tensioning operations on the molybdenum wire onhigh-speed automatic equipment. This is so because the molybdenum of theinvention has a greater degree of ductility and therefore can becold-worked without inducing stresses and strains which will causecracking and fracture.

The percentage of elongation was obtained by placing a sample wire on astandard tensile tester. The gauge length, length of wire between thetester jaws, was 10 inches and the cross head speed was 2 inches perminute.

As indicated earlier, the fill gas mixture is controlled within acertain range. It has been found, after testing the lamp shown in thedrawing inside a PAR 38 jacket, that the range of bromine can vary fromas low as 0.025% to as high as 0.075%. In the event the percentage ofbromine exceeds the upper limit, a corrosive action of the bromine onthe molybdenum parts has been observed, and if the concentration goesbelow 0.025%, the bulb wall blackens presumably because there is aninsufficient amount of halogen to combine with the evaporated tungsten.Bromine is added to the lamp of the example discussed in the form of ChBr, methyl bromide. Iodine has also been successfully used in the formof methyl iodide.

What I claim as new and desire to secure by Letters Patent of the unitedStates is:

I. A regenerative cycle incandescent halogen lamp comprising an envelopeof vitreous material with at least one pinch seal, and a mountstructure, said mount structure having outer lead-in wires connected tofoils which are hermetically sealed in said pinch seal, inner lead wiresconnected to an incandescible tungsten filament at one end and to themolybdenum foils at the other end, said envelope being filled with aninert gas and a halogengas selected from the group comprising iodine andbromine wherein the improvement comprises that the inner leads of themount structure are made of a highly ductile molybdenum better than99.95% molybdenum and having a minimum of 20% elongation.

2. The lamp claimed in claim 1 wherein said mount structure contains afilament support made of highly ductile molybdenum having a percentageof elongation which is equal to 20.

3. A lamp as claimed in claim 1 wherein said halogen gas is iodine.

4. The lamp claimed in claim 3 wherein said iodine is added to said lampas methyl iodide.

5. The lamp claimed in claim 1 wherein said halogen is bromine.

6. The lamp claimed in claim 5 wherein said bromine is added to saidlamp as methyl bromide.

1. A REGENERATIVE CYCLE INCANDESCENT HALOGEN LAMP COMPRISING AN ENVELOPEOF VITREOUS MATERIAL WITH AT LEAST ONE PINCH SEAL, AND A MOUNTSTRUCTURE, SAID MOUNT STRUCTURE HAVING OUTER LEAD-IN WIRES CONNECTED TOFOILS WHICH ARE HEMETICALLY SEALED IN SAID PINCH SEAL, INNER LEAD WIRESCONNECTED TO AN INCANDESCIBLE TUNGSTEN FILAMENT AT ONE END AND TO THEMOLYBDENUM FOILS AT THE OTHER END, SAID ENVELOPE BEING FILLED WITH AINERT GAS AND A HALOGEN GAS SELECTED FROM THE GROUP COMPRISING IODINEAND BROMINE WHEREIN THE IMPROVEMENT COMPRISES THAT THE INNER LEADS OFTHE MOUNT STRUCTURE ARE MADE OF A HIGHLY DUCTILE MOLYBDENUM BETTER THEN99.95% MOLBDENUM AND HAVING A MINIMUM OF 20% ELONGATION.
 2. The lampclaimed in claim 1 wherein said mount structure contains a filamentsupport made of highly ductile molybdenum having a percentage ofelongation which is equal to
 20. 3. A lamp as claimed in claim 1 whereinsaid halogen gas is iodine.
 4. The lamp claimed in claim 3 wherein saidiodine is added to said lamp as methyl iodide.
 5. The lamp claimed inclaim 1 wherein said halogen is bromine.
 6. The lamp claimed in claim 5wherein said bromine is added to said lamp as methyl bromide.